Spong (Ser. No. 668,495) in an application entitled "Information Record and Related Recording and Playback Apparatus and Methods" filed concurrently herewith, and incorporated herein by reference, has described an ablative recording medium which comprises a light reflective material, such as aluminum or bismuth, which is coated with a thin film of an optically absorbing organic material, such as fluorescein. A focussed modulated light beam, such as a laser beam from an argon or helium-cadmium laser, when directed at the recording medium, vaporizes or ablates the light absorbing material, leaving a hole and exposing the reflective layer. The thickness of the light absorbing layer is chosen so that the structure has minimum reflectivity. After recording there will be maximum contrast between the minimum reflectivity of the organic layer and the reflectivity of the exposed metal material. Further, when the light reflective material is itself a thin layer on a nonconductive substrate, since little energy is lost through reflection from the thin absorbing layer, and little energy is lost by transmission through the reflecting layer, the energy absorption of the light beam is concentrated into a very thin film and recording sensitivity is surprisingly high.
Ongoing work in this area has sought to improve the performance of the materials employed. Fluorescein dye, although sensitive, and producing recordings having an excellent signal to noise ratio of about 50 decibels (dB) and few, if any, dropouts or loss of signal, is hydrophilic, i.e., it absorbs moisture from the atmosphere and thus degrades after a short time at ambient atmospheric conditions. After a few days, the signal to noise ratio drops to about 35 dB and the dropouts increase to over 50 in each image. This is undesirable for commercial applications. Thus fluorescein coated recording media must be prepared shortly before use or must be carefully stored in the absence of moisture. Further, this material is soft and vulnerable to abrasion during handling. Improved organic absorbing layers should have increased toughness and should be hydrophobic, in addition to having the required optical properties such as required index of refraction and absorption coefficient.